This invention relates to a floatable impeller for multistage metal working pump and particularly for submersible pump (water-sunken pump) that has thrust bearing means movable axially along the shaft for a desired distance for reducing rotation friction between the impeller and pump shell and to facilitate assembly.
Conventional multistage centrifugal pumps (such as submersible pumps) usually have a plurality of pump shell units and impellers stacked in series along a shaft. The shaft rotates the impellers against the pump shells and generates centrifugal force for fluid to flow in the passage through the pump shells. Traditional multistage pumps made by casting is heavy, bulky and has lower pumping efficiency. They are increasing being replaced by metal working pumps.
However metal working pump shell is usually made by stamping or pressing and is difficult to reach precise dimension required. The pump shell is prone to deformation under high pumping pressure. The sealing is prone to malfunction and result in leaking. The high speed rotating impeller is easy to make friction against the stationary pump shell and result in lowering pump service life and dropping of pumping efficiency. Different fluid flow speed and volume may also cause displacement change of the impeller and result in friction against pump shell.
There are prior arts (such as ROC U.S. patent application No. 86,221,555) that propose plastic impellers for the multistage pump. The plastic impellers are floatable and axially movable along the shaft for a selected distance. While it costs less and is easier to assemble, the plastic impeller also serves as a bearing and is easily worn out under high speed friction against metallic pump shell. It also cannot be used as floatable impeller for multistage pump. There are many other prior arts being disclosed, such as U.S. Pat. Nos. 4,877,372, 5,082,425, 5,344,678, 5,425,618, 5,201,848, 5,234,317, 5,133,639, EP U.S. Pat. Nos. 04,925,71A1, 02,573,58A2, PCT No. WO. 94/23211, DE U.S. Pat. No. 44,461,93C2. All of them still do not fully resolute the problems set forth above.
It is an object of this invention to provide an improved floatable impeller for multistage metal working pump that is simple to align and position for easy assembly and has novel shaft sleeve and thrust pressure absorbing means to reduce friction between the impeller and pump shell.
It is another object of this invention to provide an improved floatable impeller that has slot recesses formed in the bearing means and thrust pressure absorbing means for collecting and discharging sand and grits in the fluid or resulting from the friction so that pumping efficiency may be improved and the pump may have longer durability.
According to this invention, the pump includes a plurality of pump shell units stacked in series along a shaft to form a multistage pump. Each pump shell unit has a metal working impeller and diffuser. The shaft rotates the impeller to draw fluid flowing from an inlet of the impeller through the diffuser across different stages of the pump.
The impeller further has an impeller hub and an impeller thrust ring. The impeller hub is integrally formed by a metallic impeller metal working member upon which the impeller is soldered on and an impeller plastic member which has a shaft bore formed therein for holding and rotating with the shaft synchronously. The impeller thrust ring includes a metallic thrust metal working member soldering on a front wall of the impeller around the inlet and a thrust plastic member mounting on the thrust metal working member.
When in use, the thrust plastic member of one pump shell unit faces against the pump shell of an adjacent pump shell unit. The friction of the thrust plastic member against the pump shell during high speed rotation of the impeller is a friction between plastic and metal. The friction wearing is less than metal to metal contact friction of conventional pump.
The diffuser is soldered to and supported by a diffuser collar. The diffuser collar includes a metallic diffuser metal working member which is integrally formed with a diffuser plastic member which in turn has a center hole to house a shaft sleeve therein. The shaft sleeve has a center bore to engage with the shaft. The shaft and shaft sleeve are rotating synchronously in the diffuser plastic member. There is a bakelite ring sandwiched between the diffuser plastic member and impeller plastic member. The structure set forth above makes rotation friction happen between plastic and plastic and may result in lower friction loss.
Furthermore there are radial slots formed in the side wall of the impeller plastic member facing the diffuser collar and the thrust plastic member remote from the thrust metal working member. And there are axial slots formed in inner side of the impeller plastic member. All those slots may collect and discharge grits and sands produced or resulting from friction between the rotating elements against the stationary element in the pump shell unit so that friction loss may be reduced, pumping efficiency may be increased and durability of the pump may be enhanced.